1. Field of the Invention
The present invention relates to a hybrid vehicle, and in particular, relates to an apparatus which increases the ability of the exhaust emission of hybrid vehicles. This application is based on Japanese Patent Application No. Hei 11-225851, the contents of which are incorporated herein by reference.
2. Description of the Related Art
Conventionally, the development of electric automobiles was advanced in order to reduce the emission of exhaust gases into the atmosphere. However, these electric automobiles, which traveled using only electrical energy, had a limited cruising range as a result of the capacity of the storage devices which stored electrical energy. In order to attain a sufficient cruising range, storage apparatuses having enormous capacity were required, and this dramatically reduced the travel performance of the vehicles.
Development has also advanced in hybrid vehicles, in which an engine is operated using fossil fuels, and the electrical energy described above is augmented with the mechanical energy of this engine, and thereby, the storage devices are reduced in size, and it is possible to obtain sufficient cruising range and vehicle travel performance.
In parallel hybrid vehicles, which are a type of hybrid vehicle, travel is conducted in such a manner as to switch between motor travel, which employs electricity, and engine travel, which utilizes fossil fuels. In such a parallel hybrid vehicle, when motor travel continues for a long period of time, as the engine is stopped during this period, no high temperature exhaust gases which are expelled by the engine while the engine is driven flow in the exhaust passage during this long period of time, and as a result the temperature of the catalyst in this exhaust passage drops, and this negatively affects the ability of the catalyst to clean the gases.
Accordingly, the temperature of the catalyst will be decreased after a long period of motor travel. In such situation, there is a problem in that if a travel mode of the hybrid vehicle is switched between engine travel and motor travel at a later time, then whenever switches to engine travel are made, the exhaust of harmful materials is increased at once after every switch.
The present invention was created in order to solve this problem, and it provides a hybrid vehicle in which a switch to a specific travel mode is made after a long period of travel by means of a motor so as to immediately increase the temperature of the catalyst, so that there is no increase in the exhaust of harmful materials.
In a first aspect of the present invention, a hybrid vehicle having a normal travel mode as a travel mode in which travel is conducted while switching between motor travel and engine travel in accordance with the degree of the depression of an accelerator, comprising: a switching device (in the embodiment described hereinbelow, a control circuit 23) being capable of switching between the normal travel mode and a specific travel mode in which travel is conducted only by means of an engine (in the embodiment described hereinbelow, an engine E) irrespective of the degree of the depression of the accelerator; an activity detector (in the embodiment described hereinbelow, a catalyst temperature sensor 18) for detecting activity of a catalyst (in the embodiment described hereinbelow, a catalyst 17) provided in the exhaust system (in the embodiment described hereinbelow, the exhaust system 16) of the engine employed in the engine travel; and a determination device (in the embodiment described hereinbelow, a control circuit 23) for determining whether or not the catalyst is activated; wherein when the determination device determines that the catalyst is not activated, the switching device compels the switching of the travel mode to the specific travel mode.
By means of the structure described above, the determination device determines whether or not the catalyst is activated, and when it determines that the catalyst is not activated, the switching device switches the normal travel mode to the specific travel mode in which the hybrid vehicle travels only by means of the engine, so that the high temperature exhaust gas travels from the engine to the catalyst provided in the exhaust system, the temperature of the catalyst increases, the catalyst becomes activated, and an increase in the exhaust of harmful materials is prevented.
In a second aspect of the present invention, the activity detector detects the activity of the catalyst when motor travel has continued for a predetermined period of time.
By means of the structure described above, when motor travel continues for a predetermined period of time in the normal travel mode, the engine is stopped during this period of time, the temperature of the catalyst decreases, and there is a great possibility that the catalyst will enter an inactive state. As a result of this, the activity of the catalyst is no longer detected. The determination device determines whether or not the catalyst is activated, and when it determines that the catalyst is not activated, the switching device switches the normal travel mode to the specific travel mode in which the hybrid vehicle travels only by means of the engine, so that high temperature exhaust gases travel from the engine to the catalyst provided in the exhaust system, the temperature of the catalyst increases, the catalyst becomes activated, and it is thus possible to prevent an increase in the exhaust of harmful materials.